Dopamine is present in a special type of cell in sympathetic ganglia. The cells are known as small intensely fluorescent cells (SIF cells) because of their appearance after histochemical staining for catecholamines. These cells modulate information transfer from preganglionic neurons to postganglionic neurons. Our present objective was to evaluate the influence of the preganglionic neurons on the metabolism of dopamine in several sympathetic ganglia of the rat. In addition, we evaluated the possible role of SIF cell dopamine metabolism on the development of hypertension in spontaneously hypertensive rats.